The subject invention relates to the etching of polyimide film. More particularly, the subject invention is a process for rapidly etching polyimide film by the use of an aqueous solution containing a basic etching component and ethyl alcohol, propyl alcohol or a combination of ethyl and propyl alcohol.
Surface etching treatments for polyimide materials are well known. It is known, for example, that the surface of polyimide film can be etched or delustered by treating the surface of the film with a solution of sodium hydroxide or potassium hydroxide in a high boiling glycol or glycol ether. Another known process for etching polyimide film comprises exposing the film to an aqueous solution of a basic compound and ethylene diamine, the latter being present in an amount in excess of its saturation point.
Another more complex process for etching polyimide film comprises coating the film with a thin layer of photoresist isoprene dimer having a viscosity of 100 to 400 centipoises at 25.degree. C.; exposing this thin layer to a heat source, thereby hardening the layer; coating the film with a second layer of a similar photoresist isoprene dimer and again heat hardening; developing both photoresist layers to remove preselected sections thereof and leave corresponding portions of the polyimide unprotected; and immersing the polyimide coated with the photoresist layer in a hydrazine bath to etch away the unprotected portions of the polyimide.
A more direct process for etching polyimide film is disclosed in U.S. Pat. No. 3,361,589 issued on the application of Lindsey. This process comprises treating the film with an aqueous solution of a basic compound and/or any lower alcohol.